Additionally, in cells with low ACE2 expression, viral infection can be enhanced by additional host factors, such as the extracellular protease BSG (also known as CD147), the transmembrane receptor NRP1 (Cantuti-Castelvetri et al., 2020), lectins (Lempp et al., 2021), or HAVCR1 phosphatidylserine receptors such TIM-1 (also known as TIMELESS) and AXL (Bohan et al., 2021; Wang et al., 2021b). Here, NRP1 is linked to viral infectious disease.